JP2003500689A - M × N optical cross connect - Google Patents

Abstract

(57) Abstract: An optical cross-connect including M first waveguides and N second waveguides is provided. The second waveguide intersects the first waveguide with a node formed at each intersection. At least one switch element (preferably an oblong resonator) is located adjacent each of the nodes and selectively transmits a portion of the signal between the waveguides. To minimize crosstalk between signals, the waveguide is expanded at or near the nodes to reduce signal diffraction.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to nanophotonic devices, and more particularly to optical cross-connect devices.

BACKGROUND OF THE INVENTION Optical switches (ie, crossbars, cross-connects, etc.) are used to solve problems such as switching, routing, interconnecting optical signals of various wavelengths propagating within an optical network. can do. Although the number of wavelengths used in a single optical signal has increased so far, it is still increasing dramatically with the widespread use of dense wavelength division multiplexing communication systems, networks and methods.

Cross-connects are known in the prior art. Furthermore, the use of cross-connects in the field of optical fibers such as wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) is also well known. However, improvements in optical cross-connects are always desired to minimize crosstalk between adjacent signals and to minimize signal loss during switching. Crosstalk is the undesired coupling of signals into the unintentional path. Therefore, in the field of optical devices, there is a need to overcome the above-mentioned drawbacks associated with the prior art.

DISCLOSURE OF THE INVENTION The above object includes M first waveguides and N second waveguides, and the second waveguides are the first waveguides. Achieved by optical cross-connects configured to intersect. A node is formed at each intersection of the first waveguide and the second waveguide, preferably with a plurality of optical switch elements arranged in the vicinity thereof. These switch elements are preferably optical devices that selectively control the signal transmission between the waveguides forming the nodes without having to convert the optical signals into electrical signals in order to achieve it. The switch element is preferably a resonator, and more preferably an oval resonator. The switch elements may be in the form of directional couplers where frequency selectivity is not a concern, or may be MEMS (microelectromechanical system) switches with mirrors.

By utilizing the present invention, each of the first and second waveguides carries an optical signal that includes one or more wavelengths. By manipulating the switch element, all or part of the optical signal can be switched from one waveguide to the other. For example, in the preferred embodiment, the resonator is tuned to couple the signal portion of a particular wavelength. This tuning is accomplished by making a controlled voltage application to the resonator using techniques known to those skilled in the art. Similarly, control is possible using a directional coupler. However, when using a directional coupler, in that state, an inactive state in which all or substantially all of the optical signals are coupled,
Alternatively, there is an active state in which all or substantially all of the optical signal bypasses the directional coupler without coupling. The voltage application causes the active state of the directional coupler.

In another aspect of the invention, the nodes in the area are increased to reduce crosstalk between signals and at the same time reduce signal loss. In particular, the waveguide is expanded at and near the node. The increased area reduces diffraction of the signal, thereby reducing losses and allowing the signal to pass through the node with less crosstalk.

Since the present invention minimizes the loss of signal switching between a plurality of waveguides, a wavelength division multiplexing transmission system (WDM) or a high density wavelength division multiplexing transmission system (DWD)
It can be used for M). Furthermore, this device can be formed as a semiconductor package, and this semiconductor package can be combined with other semiconductor devices,
It is also possible to create a single device or system. Therefore, the present invention includes features relating to the configurations and combinations of elements and component configurations,
Typical examples of these are disclosed herein. The scope of the invention is set out in the claims. The accompanying drawings are not drawn to scale and are for illustration purposes only. Like reference numerals refer to like elements throughout the drawings.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIG. 1, there is shown an optical cross connect, generally designated by the reference numeral 10. The optical cross connect 10 is formed of M first waveguides 20 and N second waveguides 30. The second waveguide 30 intersects the first waveguide 20 at the node 40, with the node 40 formed at each intersection of the first and second waveguides 20, 30. Furthermore, the optical cross-connect 10 includes at least one optical switch element 50 associated with each of the nodes 40, which switch element 50 is located near the associated node 40. In the preferred embodiment, the switch element 50 is an optical device capable of coupling an optical signal (entire signal or wavelength portion thereof) without converting the signal into an electrical signal. Switch element 50
Has two arcuate ends 51 and two substantially parallel straight portions 5 extending between them.
It is preferably an oval resonator having 2 and 2. Pending US patent application by the same inventor and assignee as the present invention The issue details an oval resonator that can be used in the present invention, the disclosure of which is incorporated herein by reference.

The optical cross connect 10 can be formed by the arbitrary numbers M and N of the first and second waveguides 20 and 30, respectively. As a non-limiting example, FIG. 1 with one each will be described. In the preferred embodiment, all components of the optical cross connect 10 are formed as a semiconductor package. As shown in FIG. 2, the devices all extend from the substrate 60 and can be integrally formed with the substrate using etching techniques known in the prior art. Therefore, the optical cross connect 10 can be formed as a semiconductor package, and this semiconductor package can be used as a “partial structural block” together with other semiconductor devices when forming a certain system. Although the first waveguide 20 and the second waveguide 30 are shown in the figure only for a limited length, it should be understood that this is to explain the operation of the device according to the invention. The optical cross connect 10 can be formed in a variety of different sizes, and the waveguides 20, 30 can also be of various lengths. In practice, the waveguides 20, 30 are often integrally formed with or welded to waveguides that extend to other systems and / or devices. Further, the light source L is 1
It produces an optical signal of one or more wavelengths, which propagates through the waveguides 20, 30. The light source L is arranged far away from the waveguides 20, 30 and the optical signal passes through other waveguides and / or optical devices and / or electro-optical devices before entering these waveguides 20, 30. To do. Note that the waveguides 20, 30 are passive devices through which optical signals can propagate in either direction. Also,
The light source L can be arranged to direct light in any one direction and in one or more of the waveguides 20, 30.

The first waveguide 20, the second waveguide 30, and the switching element 50 are described in US Pat.
, 790,583 and US Pat. No. 5,878,583, formed either as photonic wire waveguides as described and / or described, or as photonic well waveguides. In order to explain the general configuration of such a waveguide, FIG. 2 shows a typical cross section of the first waveguide 20 and the switching element 50, the second waveguide 30 being formed in the same way. It As illustrated here as a representative, a core 70 is provided surrounded by a layer of cladding 80. The core 70 is an active optical carrier medium through which optical signals propagate.

In the preferred embodiment, the straight section 52 of the oval resonator 50 is substantially parallel to the first waveguide 20. Such a linear coupling portion is formed for coupling a part of the optical signal between the oval resonator 50 and the first waveguide 20.

Referring again to FIG. 1, in use, the optical signal is propagated through at least the first waveguide 20, while the second optical signal is also propagated through the second waveguide 30. You can Each of these optical signals covers a range of wavelengths, and the optical signals can be resolved into their respective wavelength portions. A voltage is applied to the oval resonator 50 from a controllable power supply V in order to resolve the specific wavelength signal from the optical signal. In the preferred embodiment, this voltage tunes the oval resonator 50 to the desired wavelength. As the optical signal propagates through the first waveguide 20, as indicated by the arrow, a portion of the optical signal having a particular wavelength is coupled into the oval resonator 50, which in turn That portion of the signal will be coupled into the second waveguide 30.

Using techniques well known in the prior art, oval resonator 50 is formed and positioned to achieve the desired coupling. The combined portion of the optical signal will continue to propagate through the second waveguide 30 in the direction indicated by the arrow. As can be readily appreciated, the fast tuning of the oval resonator 50 allows for very accurate and selective transmission of specific wavelength signals. With respect to the second optical signal propagating through the second waveguide 30, the combined portion of the optical signal would be merely a portion of the total signal. As can be easily understood, the directions of light propagation shown here are merely for the purpose of explaining the operation of the present invention, and the signals can be transmitted in other directions without being inconsistent with the content of the invention disclosed herein. Can also be propagated to.

It should also be noted that the switch element 50 does not have to be tuned, so that it is a passive device that does not carry any portion of the optical signal propagating through the first waveguide 20. Therefore, the entire optical signal will then pass straight through the first waveguide 20. As shown in FIG. 3, at least two switch elements 50A and 50B are connected to the node 40.
Are preferably placed in close proximity to each of the. The switch elements 50A, 50B are arranged in different regions X, Y formed between the portions of the first waveguide 20 and the second waveguide 30 forming the associated node 40. Further, the switch elements 50A, 5
OBs are placed on opposite sides of node 40, referred to as a "diagonal" arrangement.

Separate voltages are applied to the switch elements 50A and 50B, respectively. Therefore, the switch elements 50A and 50B are the same as those of the first waveguide 20 and the second waveguide 3.
The portion of the optical signal that travels through both zeros can be "added" / "dropped". For example, as described above, the switch element 50A can transmit the portion of the optical signal propagating in the first waveguide 20 to the second waveguide 30. Similarly, the switch element 50B can transmit a portion of the optical signal propagating through the second waveguide 30 to the first waveguide 20. These two switch elements 50A, 5
Depending on the combination of 0B, a part of the optical signal can be added or dropped between the first and second waveguides 20 and 30. Also, one or both of the switch elements 50A, 50B are tuned to one or both signals passing straight through the node 40 and propagating through the respective first waveguide 20 or second waveguide 30. You don't have to.

To further explain the operation of the present invention, reference is made to FIG. 4 in which the numbers M and N are both two. In particular, the two first waveguides 20A, 20B are intersected by the two second waveguides 30A, 30B to form four nodes 40A-40D. In addition to this, two of the switching elements 50A to 50H are connected to the nodes 40A to 50H.
It is arranged in the vicinity of each of 40D. Similar to the above, a portion of the optical signal can be added or dropped between the first waveguide 20A, 20B and the second waveguide 30A, 30B. Table 1 shows possible operations of the optical cross-connect 10 of FIG. 4, where the switch elements 50A-50H may or may not be tuned (in Table 1, all switch elements 50A-50H). 50H are tuned to the same wavelength when they are tuned.) Table 1

As can be easily understood, an arbitrary number M of the first and second waveguides 20 and 30 is provided.
And N can be used in the same manner as described above, and signals and portions of signals can be transmitted from waveguide to waveguide to reach the desired destination. Moreover, by tuning the switch elements, different parts of the optical signal can be controllably transmitted.

The operation of the optical switch 10 according to the present invention will now be described in more detail, by way of a non-limiting example, with continued reference to FIG. Four light sources L1 to L4
Generate input signals labeled A, B, C, D which propagate through the waveguides 20A, 20B, 30A, 30B, respectively. Each of the input signals A-D can be an optical signal of multiple wavelengths or an optical signal of a single wavelength, as a matter of normal design choice. For example, the light source L1 can supply an input signal having wavelengths λ _{1 to} λ _N to the waveguide 20A. Resonator 50
If A is tuned to the wavelength λ ₁ , this wavelength is
The optical signal propagating through the waveguide 20A is coupled into the waveguide 30A. In other words, the wavelength is dropped from the optical signal in the waveguide 20A and output from the optical switch 10 via the waveguide 30A. The remaining wavelength contained in the input signal A is
It continues to propagate through 0A (ie, uncoupled wavelengths), passes through node 40, and exits optical switch 10 via waveguide 20A. The light source L3 is also a waveguide 30A
An optical signal of multiple wavelengths or a single wavelength can be provided as an input signal C to the optical signal, which optical signal is selectively coupled between two and three of the waveguides 20A, 20B, 30B. It can also pass through the waveguide 30A, depending on the selective tuning of the various resonators 50A-50H provided as part of the optical switch 10. For example, if the input signal C provided by the light source L3 comprises the wavelength λ ₁ , this wavelength may be coupled from the waveguide 30A to the waveguide 20A by the resonator 50A tuned to that wavelength. it can. Various waveguides 20A, 20B, 30A
, 30B depending on the configuration of the optical signal propagating through the resonator, and even resonators 50A-5.
Depending on the selective tuning of 0H, various other coupling configurations can be provided according to the present invention.

Referring to FIG. 5 as another embodiment, in this example, four switch elements 50I to 50L are arranged near the node 40. With these four switch elements 50I-50L, the optical signal is advantageously a waveguide 20,30.
It can pass through any of the above and can switch in either direction. In other words, a pair 201-301, 301 of adjacent portions of the waveguide 20, 30.
By providing a switch element 50 between each of -202, 202-302, 302-201, a signal or portion thereof can be switched between adjacent waveguides 20,30. By contrast, referring to FIG. 3 by way of example, the optical signal cannot be switched for regions A, B. Therefore, a signal propagating to the right through the waveguide 20 cannot be switched to propagate upward through the waveguide 30 and vice versa.

In addition to using an oval resonator as the switch element 50, an elliptical resonator 500 as shown in FIG. 6 can be used, and a circular resonator 501 as shown in FIG. 7 can be used. You can When using the elliptical resonator 500, the major axis MA of the resonator is substantially parallel to the first waveguide 20 and the minor axis NA is substantially parallel to the second waveguide 30. Is preferred. Further, the switch element 50 may be a MEMS (microelectromechanical system) switch having a mirror.

Furthermore, the switch element 50 is designated by reference numeral 5 in FIG.
A directional coupler as indicated by 02 can be used. Directional couplers are known in the prior art. Pending US patent application by the same inventor and assignee as the present invention Issue discloses an oval resonator that can be used in the present invention, the disclosure of which is incorporated herein by reference.

The directional coupler 502 includes a straight portion 503 and a curved portion 504 facing the node 40. The straight portions 503 are substantially parallel to the portions of the first waveguide 20 and the second waveguide 30, respectively. In use, the directional coupler 502 allows the entire optical signal propagating through the first waveguide 20 to be inactive (ie, no voltage applied),
It is coupled to the second waveguide 30. When a voltage is applied, the directional coupler 502
Will be activated and the entire optical signal passing through the first waveguide 20 will bypass the directional coupler without any signal coupling to the second waveguide 30. The directional coupler 502 is shaped and arranged to achieve the required coupling in the inactive state (ie, to provide the proper coupling length and coupling width between the directional coupler and the waveguide). .

In another aspect of the invention, referring to FIGS. 9A and 9B, the portion of the waveguide 20, 30 at or near node 40 is node 4
It is enlarged to increase the area of zero. Thus, each of the waveguides 20, 30 has a waveguide 20, 20 at or near the node 40.
A width w larger than the width h of the remaining portion of 30 is formed. The waveguides 20, 30 need not have the same width w or the same width h. Further, the enlarged portions of the waveguides 20, 30 may be linearly tapered portions 90 (FIG. 9A) or arcuate portions 100 (FIG. 9B).
) Can be connected to the rest of the waveguides 20, 30. The increased area reduces the diffraction caused at node 40, and thus node 4
Crosstalk of signals passing through 0 is reduced. In addition to this, signal loss is also reduced.

The first and second waveguides 20, 30 can be arranged in an orthogonal matrix arrangement, as shown in FIG. Alternatively, referring to FIG. 10, the first and second waveguides 20, 30 can be arranged such that their portions are substantially parallel. Figure 1
As shown in 0, the straight portion 110 of the first waveguide 20 is substantially parallel to the straight portion 120 of the second waveguide 30. Further, referring back to the preferred embodiment, the linear portion 52 of the oval resonator 50 is also arranged so as to be substantially parallel to the linear portions 110 and 120. With this arrangement, the oval resonator 50 has the straight portion 52 coupled to the straight portions 110 and 120, which increases the efficiency of signal transmission. In addition, the oval resonator 50 can be used to transfer signals between the first waveguide 20 and the second waveguide 30.

The various fundamental new features of the present invention applied to the above-described preferred embodiment are shown in the drawings,
Although described and pointed out, it is understood by those skilled in the art that omissions, substitutions and variations may be made to the disclosed forms and details of the invention without departing from the spirit of the invention. Will Therefore, the present invention is limited only by the scope as set forth in the appended claims.

[Brief description of drawings]

FIG. 1 is a plan view of an optical cross connect having one first waveguide and one second waveguide.

[Fig. 2]   2 is a partial cross-sectional view of the optical cross connect of FIG. 1 taken along line 2-2 of FIG. 1.

[Figure 3]   It is a top view of an optical cross connect which has two switch elements.

FIG. 4 is a plan view of an optical cross connect having two first waveguides and two second waveguides.

FIG. 5 is a plan view of an optical cross-connect having four switch elements arranged close to a single node.

[Figure 6]   It is a top view of an elliptical resonator.

[Figure 7]   It is a top view of a circular resonator.

FIG. 8 is a plan view of an optical cross connect using a directional coupler as a switch element.

FIG. 9A   FIG. 6 is a plan view showing one embodiment of a node having an enlarged area.

FIG. 9B   FIG. 9 is a plan view showing another embodiment of a node having an enlarged area.

FIG. 10 is a plan view of an optical cross connect including first and second waveguides having substantially parallel portions.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, C H, CN, CR, CU, CZ, DE, DK, DM, DZ , EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, K G, KP, KR, KZ, LC, LK, LR, LS, LT , LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, S E, SG, SI, SK, SL, TJ, TM, TR, TT , TZ, UA, UG, UZ, VN, YU, ZA, ZW (72) Inventor Ching Mikoi             United States Illinois 60091             Ilmet Elmwood Avenue             3506 (72) Inventor Hocention             United States Illinois 60090             Wheeling Picardy Lane 120 F-term (reference) 2H041 AA14 AA16 AB13                 2H047 KA03 KB01 NA01 NA10 QA01                       RA08                 2K002 AA02 AB04 AB05 BA06 DA07                       DA20 EB05 HA03

Claims (14)

[Claims] 1. A first waveguide, a second waveguide intersecting with the first waveguide in a state where a node is formed at an intersection with the first waveguide, and a node of the node. A first switch element that is disposed in the vicinity and selectively transmits at least a part of an optical signal propagating through the first waveguide to the second waveguide. Optical cross connect. 2. The optical cross connect according to claim 1, wherein the first switch element is a resonator. 3. The optical cross connect according to claim 2, wherein the resonator has an oval shape. 4. The optical cross connect of claim 2, wherein the resonator is electrically tuned to control selective transmission of at least a portion of an optical signal. 5. The optical cross connect according to claim 1, wherein the first switch element is a directional coupler. 6. A third waveguide and a fourth waveguide are further included, the second waveguide intersecting the third waveguide, and the fourth waveguide. The optical cross-connect according to claim 1, wherein the first waveguide and the third waveguide intersect with each other, and a node is formed at each intersection of the waveguides. 7. The first waveguide and the second waveguide each include a first portion near the node and a second portion farther from the node than the first portion. And wherein each of the first portion and the second portion has a width, the width of the second portion being greater than the width of the first portion. Optical cross connect. 8. The first waveguide and the second waveguide each include a third portion connecting the respective first portion of the waveguide to the second portion. The optical cross connect according to claim 7, wherein the third cross section has a taper. 9. Each of the first waveguide and the second waveguide includes a third portion connecting the respective first portion of the waveguide with the second portion. The optical cross connect according to claim 7, wherein the third portion has an arcuate shape. 10. At least one second disposed near the node for selectively transmitting at least a portion of an optical signal propagating through the second waveguide to the first waveguide. Further including a switch element, the first switch element being disposed in a first region formed between the first waveguide and the second waveguide portion, the second switch element being A switching element disposed in a second region formed between the first waveguide and the second waveguide portion, the first waveguide and the second waveguide being provided. The optical cross connect according to claim 1, wherein at least one of the two is arranged between the first switch element and the second switch element. 11. The optical cross-connect of claim 10, further comprising a switch element disposed between adjacent portions forming each pair of the waveguides. 12. The first waveguide, the second waveguide, and the first switch element are integrally formed as a semiconductor package. Optical cross connect described. 13. The optical cross connect according to claim 1, wherein the portion of the first waveguide is arranged substantially parallel to the portion of the second waveguide. 14. The optical cross connect according to claim 12, wherein the switch element is arranged between parallel portions of the first waveguide and the second waveguide. .